sass-theme-map-function.scss

$color-primary: purple;
$color-secondary: blue;
$color-support: green;

$theme-colors: (
  primary: $color-primary,
  secondary: $color-secondary,
  support: $color-support
);

@function theme-color($key) {
  @return map-get($theme-colors, $key);
}

@debug theme-color(primary);
// output: Line 15 CSS: purple

h1 {
  color: theme-color(primary);
}

site.html

<h1>Hello World</h1>